<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="box">
franbkk
</div>
<script>
    var box = document.getElementById('box');
    //
    //可读，可写

    var s = "<script>alert('a')<\/script>"
    box.innerHTML = s;//可写，可以被赋值,

</script>
</body>
</html>